A disturbance (change in position or state of individual particles) in the fabric of space-time causes a sphere of influence. Stated in a simplistic manner, the action of one particle influences the actions of the others near it. This sphere of influence is referred to as a "field", and this field is designated as either electric or magnetic (after the way it influences other particles). The direction of travel of the particle is called the direction of propagation. The propagation of the particle, the sphere of influence, and the way it influences other particles is called an electromagnetic wave, and is shown in FIG. 1.
As shown in FIG. 1, the electric and magnetic fields are orthogonal (at right angles) to each other and the direction of propagation. These fields can be mathematically expressed as a vector quantity (indicating the direction of influence along with strength, i.e., magnitude, of influence) at a specific point or in a given region in space. Thus, FIG. 1A is the electromagnetic wave in FIG. 1, but with the view of looking down the axis of propagation, that is, down the x axis of FIG. 1. FIG. 1A shows some possible various electric field vectors that could exist, although it should be understood that any and all possible vectors can exist around the circle, each having different magnitudes.
Vectors can be resolved into constituent components along two axes. This is done for convenience sake and for generating a frame of reference that we, as humans, can understand. By referring to FIG. 1B, it is shown that the electric field vector E, can be resolved into two constituent components, E(y) and E(x). These quantities, then, describe the orientation and the magnitude of the electric field vector along two axes, the x and y, although other axes or systems could be chosen. The same applies to magnetic fields, except that the X and Z axes would be involved.
The way the electric and magnetic fields vary with time in intensity and direction of propagation have been determined by several notable mathematicians and physicists, culminating in a group of basic equations by James Maxwell. These equations, simply applied, state that a field vector can be of one of several different states, that is: 1) the field vector varies randomly over a period of time, or 2) the field vector can change directions in a circular manner, or 3) the field vector can change directions in a elliptical manner, or 4) the field vector can remain constant in magnitude and direction, hence, the field vector lies in one plane, and is referred to as planar.
This orientation of a field vector and the way it changes with time is called the state of polarization.
Electromagnetic waves can be resolved into separate electromagnetic waves with predetermined orientations of a field vector. The electromagnetic waves with a predetermined orientation of a field vector can then be directed through materials, such as a liquid crystal device, that is capable of changing (or altering) their orientation of the field vector upon application of an outside stimulus, as is demonstrated in FIG. 3. These devices are noted as programmable electromagnetic wave field orientation rotating devices (PEMFVORD).
An electromagnetic wave can be characterized by its frequency or wavelength. The electromagnetic spectrum (range) extends from zero, the short wavelength limit, to infinity, the long wavelength limit. Different wavelength areas have been given names over the years, such as cosmic rays, alpha rays, beta rays, gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, TV and FM radio, short wave, AM, maritime communications, etc. All of these are just short hand expressions of stating a certain range of frequencies for electromagnetic waves.
Different areas of the spectrum interact with electromagnetic influences upon them in various proportions, with the low end being more influenced by magnetic fields, and the high end being influenced by electric fields. Thus to contain a nuclear reaction, a magnetic field is used, while controlling light an electric field is used.
In particular, image display systems such as video projectors utilize liquid crystal devices (LCD) acting as a PEMFVORFD for displaying a projected image. A PEMFVORD for a video projector is typically formed as a LCD having a matrix of individual cells or pixels (picture elements) arranged in a checkerboard array (see FIG. 2A). In general, the LCD is placed in a polarized (a single orientation of the electromagnetic wave electric field vector) light path and control is effected by altering the optical transmission characteristics (i.e, the birefringence) for each cell by the response to an applicable stimulus. The individual cells alter the polarization (change by rotating the polarization state or orientation of the electromagnetic wave electric field vector) of the individual cells or pixels according to the information that is desired to be finally portrayed as the projected image. The resolution of the projected image depends upon several factors, including the number of cells in the LCD. A display of 320 horizontal pixels by 240 vertical pixels will have a generally rectangular peripheral shape and yield a display of 76,800 pixels. A typical television set for the United States market is composed of 115,000 pixels (i.e., combination of red, blue and green dots in a television receiver). A light aperture for admitting light to the array of cells for the display generally is of a rectangular shape.
FIG. 2 illustrates a schematic cross section of an LCD cell. The LCD cell 100 includes a liquid crystal material 101 that is contained between two transparent plates 103, 104. Spacers 105, 106 are used to separate the transparent plates 103, 104. Sealing elements 107, 108 seal the liquid crystal material 101 between the transparent plates 103, 104. Conductive coatings 109, 110 on the transparent plates 103, 104 conduct the appropriate electrical signals to the liquid crystal material 101.
A type of liquid crystal material 101 used in most LCD cells for optical display systems is referred to as "twisted nematic." In general, with a twisted nematic LCD cell, the molecules of an LCD cell are rotated in the absence of a field through a 90.degree. angle between the upper 103 and lower 104 transparent plates. When a field is applied, the molecules are untwisted and line up in the direction of the applied field. The change in alignment of the molecules causes a change in the birefringence of the cell. In the homogeneous ordering, the birefringence of the cell changes from large to small whereas the opposite occurs in the homeotropic case. The change in birefringence causes a change in the orientation of the electric field vector for the light being passing through the LCD. The amount of the rotation in the molecules for an individual LCD cell 100 will determine how much change in polarization (orientation of the electric field vector) of the light occurs for that pixel. The light beam is then passed through another component of the system (i.e., polarizer analyzer) and is resolved into different beams of light by the orientation of their electric field vectors, with the light that has a selected predetermined component of the electric field vector passing through to finally strike the screen used for the display.
A twisted nematic LCD cell requires the light incident at the LCD cell 100 to be polarized. The polarized light for a typical projector is generally derived from a randomly polarized light source that is collimated and then filtered by a plastic polarizer to provide a linear polarized beam. Linear polarized beams are conventionally referred to as being S-polarized and P-polarized with the P-polarized beam defined as polarized in a direction parallel to the plane of incidence and the S-polarized beam defined as polarized perpendicular to the plane of incidence.
The development of PEMFVORD technology has resulted in the development of LCD projectors which utilize one or more LCDs to alter the orientation of the electric field vector (see FIG. 3) of the light being projected. The birefringence of the individual LCD pixels are selectively altered by suitable apparatus such as cathode ray tubes, lasers, or electronic circuit means. A typical LCLV projector includes a source lamp which is used to generate a light beam that is directed through a polarizer. This polarized light is directed through the LCDs to change the polarization according to the image to be displayed. The light, after exiting the LCD, passes through a plastic polarizer analyzer which stops and absorbs the unwanted portion of light. The formed image is then enlarged with a projection lens system for forming an enlarged picture on a display screen.
Color LCLV projectors typically include color separating apparatus such as a prism, beam splitters or dichroic mirrors to separate collimated white light beams from the light source into three primary color beams (i.e., red, green and blue beams). The red, green and blue beams are then individually modulated by LCDs and combined by separate optical apparatus such as combining prisms, mirrors or lenses.
Representative prior art LCLV projectors are disclosed in U.S. Pat. No. 5,060,058 to Goldenberg, et al., U.S. Pat. No. 5,048,949 to Sato, et al., U.S. Pat. No. 4,995,702 to Aruga, et al., U.S. Pat. No. 4,943,154 to, Miyatake, et al., U.S. Pat. No. 4,936,658 to Tanaka, et al., U.S. Pat. No. 4,936,656 to Yamashita, et al., U.S. Pat. No. 4,935,758 to Miyatake, et al., U.S. Pat. No. 4,911,547 to Ledebuhr, U.S. Pat. No. 4,909,601 to Yajima, et al., U.S. Pat. No. 4,904,061 to Aruga, et al., U.S. Pat. No. 4,864,390 to McKechnie, U.S. Pat. No. 4,861,142 to Tanaka, et al., U.S. Pat. No. 4,850,685 to Kamakura, U.S. Pat. No. 4,842,374 to Ledebuhr, U.S. Pat. No. 4,836,649 to Ledebuhr, et al., U.S. Pat. No. 4,826,311 to Ledebuhr, U.S. Pat. No. 4,786,146 to Ledebuhr, U.S. Pat. No. 4,772,098 to Ogawa, U.S. Pat. No. 4,749,259 to Ledebuhr, U.S. Pat. No. 4,739,396 to Hyatt, U.S. Pat. No. 4,690,526 to Ledebuhr, U.S. Pat. No. 4,687,301 to Ledebuhr, U.S. Pat. No. 4,650,286 to Koda, et al., U.S. Pat. No. 4,647,966 to Phillips, et al., U.S. Pat. No. 4,544,237 to Gagnon, U.S. Pat. No. 4,500,172 to Gagnon, U.S. Pat. No. 4,464,019 to Gagnon, U.S. Pat. No. 4,464,018 to Gagnon, U.S. Pat. No. 4,461,542 to Gagnon, U.S. Pat. No. 4,425,028 to Gagnon, U.S. Pat. No. 4,191,456 to Hong, et al., U.S. Pat. No. 4,127,322 to Jacobson, et al., U.S. Pat. No. 4,588,324, to Marie, U.S. Pat. No. 4,943,155 to Cross, Jr., U.S. Pat. No. 4,936,657 to Tejima, et al., U.S. Pat. No. 4,928,123 to Takafuji, U.S. Pat. No. 4,922,336 to Morton, U.S. Pat. No. 4,875,064 to Umeda, U.S. Pat. No. 4,872,750 to Morishita, U.S. Pat. No. 4,824,210 to Shimazaki, U.S. Pat. No. 4,770,525 to Umeda, et al., U.S. Pat. No. 4,715,684 to Gagnon, U.S. Pat. No. 4,699,498 to Naemura, et al., U.S. Pat. No. 4,693,557 to Fergason, U.S. Pat. No. 4,671,634 to Kizaki, et al., U.S. Pat. No. 4,613,207 to Fergason, U.S. Pat. No. 4,611,889 to Buzak, U.S. Pat. No. 4,295,159 to Carollo, et al.
Various prior art techniques and apparatus have been heretofore proposed to present 3-D or stereographic images on a viewing screen, such as on a polarization conserving motion picture screen. See U.S. Pat. No. 4,955,718 to Jachimowicz, et al., U.S. Pat. No. 4,963,959 to Drewio, U.S. Pat. No. 4,962,422 to Ohtomo, et al., U.S. Pat. No. 4,959,641 to Bess, et al., U.S. Pat. No. 4,957,351 to Shioji, U.S. Pat. No. 4,954,890 to Park, U.S. Pat. No. 4,945,408 to Medina, U.S. Pat. No. 4,936,658 to Tanaka, et al., U.S. Pat. No. 4,933,755 to Dahl, U.S. Pat. No. 4,922,336 to Morton, U.S. Pat. No. 4,907,860 to Noble, U.S. Pat. No. 4,877,307 to Kalmanash, U.S. Pat. No. 4,872,750 to Morishita, U.S. Pat. No. 4,870,486 to Nakagawa, U.S. Pat. No. 4,853,764 to Sutter, U.S. Pat. No. 4,851,901 to Iwasaki, U.S. Pat. No. 4,834,473 to Keyes, et al., U.S. Pat. No. 4,807,024 to McLaurin, et al., U.S. Pat. No. 4,799,763 to Davis, U.S. Pat. No. 4,772,943 to Nakagawa, U.S. Pat. No. 4,736,246 to Nishikawa, U.S. Pat. No. 4,649,425 to Pund, U.S. Pat. No. 4,641,178 to Street, U.S. Pat. No. 4,541,007 to Nagata, U.S. Pat. No. 4,523,226 to Lipton, et al., U.S. Pat. No. 4,376,950 to Brown, et al., U.S. Pat. No. 4,323,920 to Collendar, U.S. Pat. No. 4,295,153 to Gibson, U.S. Pat. No. 4,151,549 to Bautzc, U.S. Pat. No. 3,697,675 to Beard, et al. In general, these techniques and apparatus involve the display of polarized or color sequential two-dimensional images which contain corresponding right eye and left eye perspective views of three-dimensional objects. These separate images can also be displayed simultaneously in different polarizations or colors. Suitable eyeware, such as glasses having different polarizing or color separating coatings, permit the separate images to be seen by one or the other eye. This type of system is relatively expensive and complicated requiring two separate projectors and is adapted mainly for stereoscopic movies for theaters. U.S. Pat. No. 4,954,890 to Park discloses a representative projector employing the technique of alternating polarization.
Another technique involves a timed sequence in which images corresponding to right-eye and left-eye perspectives are presented in timed sequence with the use of electronic light valves. U.S. Pat. No. 4,970,486 to Nakagawa, et al., and U.S. Pat. No. 4,877,307 to Kalmanash disclose representative prior art stereographic display systems of this type.
While previous time sequential light valve systems are adaptable to display arrangements for a television set, because of problems associated with color, resolution and contrast of the projected image, they have not received widespread commercial acceptance. Moreover, the systems proposed to date have also been relatively expensive and complicated.